Rocking mill

ABSTRACT

A rocking mill of the kind including grinding tubes in a spaced horizontal layout, is given a compact and efficient layout by operating the grinding tubes from a drive centre disposed centrally within the tubes and the supporting frame thereof.

United States Patent Gammerler et a1.

ROCKING MILL Inventors: Hagen Gammerler, 8021 lcking,

lcking; Harald Bohm, 8021 Deining, Deining, both of Germany Filed: Apr. 19, 1973 Appl. No.: 352,540

Foreign Application Priority Data Apr. 21, 1972 Germany 221975 US. Cl 241/170, 241/171, 241/175,

241/285 R Int. Cl. B02C 17/14, B020 17/24 Field of Search 741/170, 171, 175, 192,

[451 Feb. 11, 1975 [56] References Cited UNITED STATES PATENTS 2,760,729 8/1956 Mittag et a1. 241/175 X 3,310,245 3/1967 Decker et a1. 241/175 X 3,552,068 1/1971 Van Fossen 241/175 X Primary Examiner-Roy Lake Assistant Examiner-E. F. Desmond 6 Claims, 9 Drawing Figures it mu 12 13 V 3 9 n 76 g 77 i 75 i i 2 i l A I I Y i: i: i 'i 3i 1! 11/1! i: 57

PATENTED FEB] 1 I975 SHEET 1 BF 4 FIG. 7

PATENTEDFEBHIQYB 3,865,318-

SHEET 2 OF 4 v PATENTEB FEB! 1 I975 SHEET 3 [IF 4 FIG. '4

raw ICEWLGW ROCKING MILL This invention relates to a rocking mill for grinding solid bodies, particularly fine rock, of the form comprising a plurality of grinding tubes containing grinding rods, grinding balls or like grinding ancillaries, held by support plates on a bed frame, and comprising a driving unit.

Rocking mills of this kind are not only suitable for dry grinding but for wet grinding also; they can be used effectively both as coarse grinding machine and fine grinding machines for continuous operation in many branches of industry.

A known form of rocking mill equipped with three grinding tubes has the driving unit arranged at the side thereof, and this sets the grinding tubes into a rocking motion through a driving shaft. Because of the cardan shafts which have to be interposed, after an extended period of operation the stress imposed on the driving shaft differs somewhat between the end thereof nearest the driving unit and the end most remote from this unit, as a consequence of the heavy masses which are set into oscillation, and this substantially reduces the efficiency of the mill.

it is an object of this invention to provide a rocking mill which is of more efficient construction and operation.

In pursuance of this object, in the present invention the driving unit comprises a driven part which is ar ranged in the area.

Quite apart from the facts that this confers a considerable technical advantage in increasing the length of effective life of the machine and the need for mainte nance of the various machine parts is reduced, the arrangement also provides for ready access to all the openings in the grinding tubes, whether the inlet openings thereof are arranged below one another or the covers are disposed at both ends of the tubes, these having to be opened each time the mill is checked, the grinding bodies are charged thereinto, or the worn parts are replaced. I

In accordance with a preferred form of the invention, the driven part is a shaft which is supported centrally within the area defined by the support plates and is flanked by cardan half-shafts disposed symmetrically in relation thereto and drivingly coupled to mechanism for oscillating said grinding tubes. The driven part is not directly coupled to the power unit but may be driven, for example, through a V-belt and pulley arrangement. Thus the possibility of varying the rate of rotation and allows for the introduction of appropriate connections controlling the running.

In accordance with a preferred embodiment of the invention more than three, and preferably four, grinding tubes are provided and are arranged in a polygonal, for example rectangular, arrangement. Further, the said mechanism is mounted in the support plates through the agency of spherical bearings. The mounting in normal roller bearings has been found not to be particularly successful because in the event of slight deviation of of the oscillating masses from the vertical plane passing through the shaft, roller bearings of this character are easily damaged.

Advantageously the rocking mill is mounted on a frame composed of two transoms parallel to the grinding tubes, and transverse brackets and draws rods extending between said transoms. This particular construction of the mill affords the addition of a very strong and rigid structure. The undesirable shifting of the transoms, which is unavoidable in known rocking mills, is completely eliminated with the structure provided in this invention. The use of draw rods associated with the transverse brackets prevents an uncontrollable force being transmitted from the rocking mill to the foundation on which it is mounted. Since a rocking mill, for example, when fully loaded and in operation can weigh up to 60 tons, it will be understood that it is very desirable to have a controllable distribution of force to the foundation thereof. With the use of the draw rods mentioned above, only vertical compression forces and horizontal shear forces are transmitted to the foundation and these can be pre-calculated without difficulty.

Preferably sets of rubber buffers are provided at the transverse brackets, and these are in each case composed of two cooperating confronting rubber elements. This method of cushioning the structure means that the mill cannot swing so far out as in known arrangements.

The rubber elements in each case maycomprise two cylindrical sections in contact with one another and a retaining member extending approximately at right angles thereto. The use of such cup-like elements caters for a very high degree of dampening down of the vibrations in the mill.

The grinding tubes can be provided at one end at least with a screwed cover and a closure cap independent thereof. The screwed cover can be held on the grinding tube through the agency of two removable bolts, one at least of which may be used as a hinge. The closure cap referred to may have a slotted plate mounted thereon with the intermediary of spacer mem bers, and the closure cap is preferably provided with at least one centering part. The separation of the screw means, the closure wall and the slotted plate or slotted wall means, in the first place and as already stated, allow ready removal of the screw means, and, on the other hand, a firm and accuratelycentred application of the closure cap. Whilst it has hitherto been usual to fasten the so-called slotted plates or slotted walls to the end of the grinding tubes by means of a set of screws, the method of closure of the tubes in accordance with this invention provides for a ready opening and closing thereof. Thus a tube, when use is made of a closure in accordance with the present invention, can, for example, be opened by an attendant in a quarter of an hour,

whereas the same job normally has to be carried out by two people and takes one hour. It is also possible for the grinding tubes of the mill in this invention to be selectively coupled together.

For this purpose at least two discharge pipe sections can be arranged at the ends of each of thegrinding tubes. This facility, in conjunction with a variable supply arrangement, caters for various systems which will permit various programmes to be carried out in the grinding mill, as will be disclosed below in more detail.

In accordance with a further feature of the invention a replaceable grid, sieve, or the like can be provided in each grinding tube and extends in the longitudinal direction of the latter, being disposed on a frame which comprises strutts, bars or the like extending in the longitudinal or transverse direction of the tube. The grid is used to separate fine and very fine material during the actual grinding operation. The grinding bodies, for example, grinding bars, admittedly in this case operate in a reduced part of the cross-section of the grinding tube, but this has not been found unfavourable because the sieving out of the fine or very fine material facilitates the operation of grinding the original material.

The grid is preferably disposed loosely on the frame, which permits it to be replaced without. for example, any attachment means having to be unfastened on the grinding tubes.

Very conveniently the longitudinal edges of the grid or the like serve as a mounting for a lining body for the tube in the form of a parallel cylindrical slidable component. The frame can, alternatively, be connected to the grinding tube, and it is possible for at least the longitudinal margins of the grid to be thickened to constitute support beams.

An example of a rocking mill according to the inven- -tion is illustrated in the accompanying drawings, in

which,

FIG. I is a perspective illustration of the mill,

FIG. 2 is a longitudinal section through this mill,

FIG. 3 is an end view of the same,

FIG. 4 is an operating diagram,

FIG. 5 is a perspective and enlarged illustration of a detail of the mill,

FIG. 6 shows another detail,

FIG. 7 is a scrap section through yet another detail,

FIG. 8 is a section through a grinding tube, and

FIG. 9 is a perspective illustration of part of the same.

The rocking mill has four grinding tubes 1 to 4. Theses tubes are mounted by support plates 6 secured to a frame which will be described in more detail later. The power unit used is a motor 7 which rotates a driven shaft 9 through the agency of a V-belt 8. The shaft 9 has a V-pulley l0 and is connected to two double cardan shafts 11 and 12 which are arranged symmetrically in relation to the V-pulley which can here be regarded as the driven part.

Shaft 9 is mounted in bearings I3. These bearings 13 are carried by uprights l4 firmly secured to the frame 5. Consequently, when the drive is applied, those parts up to the double cardan shafts l1 and 12 do not oscillate with the shaft 9.

Rocker plates 16 and 17 are provided in independent casings l5 beyond the double cardan shafts 11 and 12 and are rigidly connected to shaft 9. Special spherical roller bearings are provided to mount the part of shaft 9 between the rocker plates l5, l6, and this will be more fully explained in connection with FIG. 7.

The individual grinding tubes are supplied with material to be crushed through hose-type connections 21 from a pouring opening at the top of the mill. All four tubes 1 to 4 are fed simultaneously in the usual way.

Provided at the two ends of each of the grinding tubes 1 to 4 are discharge pipe sections 22, and in the embodiment illustrated there are two sections 22 at each end of the tube. Hose-type connections 23 can be coupled to these pipe sections and connected to a common outlet 24.

The discharge pipe sections 22, arranged as they are in pairs, cater for various modes of connection and hence different operating schemes, as in the examples diagrammatically illustrated in FIG. 4, In the case of scheme A the individual grinding tubes are in each case individually fed, illustrated in FIG. I, and individually emptied as can also be seen from FIG. 1.

It is possible, however, as can be seen from scheme B, to arrange for unilateral charging of the grinding tubes at one end to use the opposite end of the grinding tube concerned as a discharge end.

In scheme C the grinding tubes of the four are coupled together in two pairs so that two different grinding can be carried out simultaneously by supplying them with different qualities of material for example material of different degrees of fineness.

Finally, in scheme D three grinding tubes are connected together and the fourth tube can be used for a finishing grinding phase.

As can be seen from FIG. 3 the base frame 5 comprises transoms 25 which are diposed parallel to the grinding tubes 1-4 and are connected together by cross-brackets 26 at the level of the support plates 6. These brackets 26 cater for very firm mounting of the complete rocking mill. In each case the action of the cross-bracket is reinforced by a draw bar 27 and the forces generated by the rocking mill in operation are transmitted through the transoms 25 either vertically into the foundation which may be provided, or as pure shear components at right angles thereto. Since these two components of force can be accurately calculated for the complete assembly, the foundation conditions can be checked.

The grinding tubes, which can be filled with grinding rods, grinding balls or other grinding elements, are closed at both ends by closure caps 40 with screwed covers 30. As can be seen from FIG. 1 the screwed covers comprise plates 31 which have ears 32 at the opposite edges. Corresponding ears 34 are provided at the ends of the grinding tubes and bolts 33 are passed through the associated cars 32 and 34 to provide a secure connection between the grinding tube and the screwed cover. Machine nuts 35 are provided to fasten the screw covers. As can be seen from FIG. 5 a bolt 33 can be extracted from these ears to enable the screw cover 30 concerned to be turned on the other bolt 33.

Whilst a connection of a screw cover to the corresponding closure cap 40 does not have to be provided, it is possible see FIG. 5 to make a connection of this kind using a frame part 41 which is pivotally coupled to the closure cap 40 through the agency of a bolt 42.

As can be seen from FIG. 2, the closure cap 40 is provided with a known type of slotted wall or slotted plate 44 through the agency of a spacer 43. Material from the tube can be sieved through these slots. The closure cap 40 is firmly connected to the slotted plate 44 through spacer elements 43, so that the slotted plate will move with the closure cap when this is swung outwards (FIG. 5). This plate is replaceable in the usual way and can be exchanged for plates catering for varying sizes of ground product.

The provision for ready pivoting of the closure cap is important because it is advantageous for the wear cylinders 45, which are installed in the grinding tubes, to be as readily accessible as possible.

The rocking mill is resiliently mounted on the bed frame 5 through the agency of rubber buffers 50. In the apparatus illustrated these buffers are provided at the four corners of the mill. two pairs of rubber elements SI being provided at each corner. These rubber elements are of cylindrical cross-section in their relaxed condition and have a metal backing to hold the rubber parts on mountings 52.

Two pairs of rubber elements are superposed one on another in each set, so that there are four sets of rubber elements at each corner of the mill. FIG. 6 shows the rubber elements compressed. The contact surfaces of the rubber elements 51 (which are cylindrical form in the relaxed condition) are of ring shape in the compressed condition and the rings 53 so defined are of a substantially larger diameter than the original cylindrical section.

As has already been stated a so-called spherical roller bearing is arranged at the sides of the rocker plates 16 and 17 to provide a very secure and long wearing mounting of shaft 9. One such bearing is illustrated in FIG. 7.

It comprises two bearing race elements 60, 61 having rounded openings to receive the individual spherical rollers 62, the outer element 60 having a spherical cavity and the inner bearing body 61 two mirror image recesses 63, 64 in which the individual spherical rollers 62 run. These recesses 63, 64 are so shaped that the spherical rollers 62 cannot escape laterally through wall parts 65, 66. A roller cage 67 of substantially triangular section is provided between the spherical rollers 62 and the latter run in a path inclined to the central axis of the bearing. This cage 67 serves for the internal support of the rollers and maintains them in their inclined disposition. Fingers 68 entering the individual rollers 62 are provided on cage 67.

An example of the grinding tube 1 illustrated in FIG. 8 comprises a steel body 72, for example 12 mm in thickness, which receives a liner 73 which only extends around part of the cross-section of the tube. The grinding bodies, for example the grinding bars, have been omitted from this drawing. In the embodiment illustrated in FIG. 8 the grinding tube is assumed to have a free internal diameter of about 53 cm. and may have a length of about 2 m.

The liner body 73 can be of standard tubular form, and again for example 12 mm. thick, and can be slid within the grinding tube. This liner tube can be composed of a number of separate parts. The liner body in the version illustrated in FIGS. 8 and 9 is of different construction from the normal and consists merely ofan upper part 73. The liner body is omitted in the area below a grid (described in more detail below) which is provided in the tube. The upper part 73 is displaceable in the grinding tube 1 and held in the latter by a small inherent resilience without any special fastening means being necessary. The grid referred to above is shown at 76 and is for example of steel with a thickness of about mm. It is used for the separation of fine or very fine product and is freely mounted on a frame 80 in the tube or can be fastened to the latter. This frame 80 has feet 81 which can be connected to the lower section 75 of the grinding tube, but do not have to be, and comprises longitudinal bars 82 and cross-bars 83.

The grinding tube I could be made in two parts, the lower part 75 being made separately from the upper part and accommodating the frame 80. This unit then constitutes a self-contained unit as illustrated in FIG. 9. The grid 76 can either be inserted in the grinding tube l separately from frame 80 or, if it is difficult to sepa rate it from the frame 80, the grinding tube 1 is first furnished with the upper part 74 of the lining and this. as already mentioned. is held in grinding tube I without any fastening means. Then the frame 80 with the grid 76 is slid into the grinding tube and connected to the lower part of the latter.

In another arrangement the lower part 75 of the grinding tube, connected to frame 80, is coupled with the upper part of the grinding tube and only then is the upper part 74 of the lining slid in. It is of no consequence whether the grid 76 is connected to frame or represents a separate and replaceable part.

In the arrangement illustrated in FIG. 8 the longitudinal edges of the grid are rigidly connected to the corresponding lower part 75 of the tube body; this however is not absolutely essential. The longitudinal edges of the grid have a bevel 91 which extends approximately radially and serves to position the upper part 74 of the lining body.

Advantageously at least the longitudinal margins of the grid are thickened to provide a beam so that the bevel referred to above represents a part of this beam; the transverse margins could be similarly thickened.

We claim:

1. In a rocking mill for grinding solid materials, comprising a bed frame, support plates upstanding from said bed frame, a plurality of grinding tubes containing grinding elements mounted by said support plates, mechanism for oscillating said tubes, and a driving unit for actuating said mechanism, the improvement wherein the driving unit includes a driven part comprising a shaft centrally supported within the area defined by the support plates, eardan half shafts at each end of the shaft, symmetrically disposed with respect to the shaft and drivingly coupled to said mechanism.

2. A rocking mill according to claim I, in which said mechanism is mounted in the support plates through the agency of spherical bearings.

3. A rocking mill according to claim I, in which the grinding tubes are provided at one end at least with a screwed cover and a closure cap independent thereof. and the screwed cover is held on the grinding tube through the agency of removable bolts, one at least of which may be used as a hinge.

4. A rocking mill according to claim 3, in which the closure cap has a slotted plate mounted thereon with the intermediary of spacer members, and is provided with at least one centering part.

5. A rocking mill according to claim 1, in which at least two discharge pipe sections are arranged at the end of each of the grinding tubes to enable them to be selectively connected together. I

6. A rocking mill according to claim 1, further comprising a replaceable grid in each grinding tube and extending in the longitudinal direction of the latter, and a frame supporting this grid, said frame comprising bars extending in the longitudinal and/or transverse direction of the tube, and a partly cylindrical lining .body

supported on said frame. 

1. In a rocking mill for grinding solid materials, comprising a bed frame, support plates upstanding from said bed frame, a plurality of grinding tubes containing grinding elements mounted by said support plates, mechanism for oscillating said tubes, and a driving unit for actuating said mechanism, the improvement wherein the driving unit includes a driven part comprising a shaft centrally supported within the area defined by the support plates, cardan half shafts at each end of the shaft, symmetrically disposed with respect to the shaft and drivingly coupled to said mechanism.
 2. A rocking mill according to claim 1, in which said mechanism is mounted in the support plates through the agency of spherical bearings.
 3. A rocking mill according to claim 1, in which the grinding tubes are provided at one end at least with a screwed cover and a closure cap independent thereof, and the screwed cover is held on the grinding tube through the agency of removable bolts, one at least of which may be used as a hinge.
 4. A rocking mill according to claim 3, in which the closure cap has a slotted plate mounted thereon with the intermediary of spacer members, and is provided with at least one centering part.
 5. A rockIng mill according to claim 1, in which at least two discharge pipe sections are arranged at the end of each of the grinding tubes to enable them to be selectively connected together.
 6. A rocking mill according to claim 1, further comprising a replaceable grid in each grinding tube and extending in the longitudinal direction of the latter, and a frame supporting this grid, said frame comprising bars extending in the longitudinal and/or transverse direction of the tube, and a partly cylindrical lining body supported on said frame. 